-
[show abstract]
[hide abstract]
ABSTRACT: A vacuum-sealed miniature X-ray tube based on a carbon nanotube field-emission electron source has been demonstrated. The diameter of the X-ray tube is 10 mm; the total length of the tube is 50 mm, and no external vacuum pump is required for the operation. The maximum tube voltage reaches up to 70 kV, and the X-ray tube generates intense X-rays with the air kerma strength of 108 Gy * cm2 min1. In addition, X-rays produced from the miniature X-ray tube have a comparatively uniform spatial dose distribution.
Nanoscale Research Letters 05/2012; 7(1):258. · 2.73 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Stable carbon nanotube (CNT) field emitters for a vacuum-sealed miniature X-ray tube have been fabricated. The field emitters
with a uniform CNT coating are prepared by a simple drop drying of a CNT mixture solution that is composed of chemically modified
multi-walled CNTs, silver nanoparticles, and isopropyl alcohol on flat tungsten tips. A highly thermal- and electrical-conductive
silver layer strongly attaches CNTs to the tungsten tips. Consequently, the field emitters exhibit good electron emission
stability: continuous electron emission of around 100μA at 2.3V/μm has stably lasted over 40h even at non-high vacuum ambient
(~10−3Pa).
KeywordsCarbon nanotube-Field emission-Drop drying-Miniature X-ray tube
Nanoscale Research Letters 05/2012; 5(4):720-724. · 2.73 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A simple and straightforward approach to prepare TiO2-coated carbon nanotubes (CNTs) is presented. Anatase TiO2 nanoparticles (NPs) with the average size ~8nm were coated on CNTs from peroxo titanic acid (PTA) precursor even at low
temperature of 100°C. We demonstrate the effects of CNTs/TiO2molar ratio on the adsorption capability and photocatalytic efficiency under UV–visible irradiation. The samples showed not
only good optical absorption in visible range, but also great adsorption capacity for methyl orange (MO) dye molecules. These
properties facilitated the great enhancement of photocatalytic activity of TiO2 NPs-coated CNTs photocatalysts. The TiO2 NPs-coated CNTs exhibited 2.45 times higher photocatalytic activity for MO degradation than that of pure TiO2.
KeywordsTiO2
-Carbon nanotubes-Nanoparticles-Photocatalyst-Methyl orange
Nanoscale Research Letters 04/2012; 5(3):603-607. · 2.73 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The photoelectrochemical (PEC) responses of electron-irradiated [6,6]-phenyl-C61-butyric acid methyl ester (PCBM)/TiO2 electrodes were evaluated in a PEC cell. By coating PCBM on TiO2 nanoparticle film, the light absorption of PCBM/TiO2 electrode has expanded to the visible light region and improved the PEC responses compared to bare TiO2 electrode. The PEC responses were further improved by irradiating an electron beam on PCBM/TiO2 electrodes. Compared to non-irradiated PCBM/TiO2 electrodes, electron irradiation increased the photocurrent density and the open-circuit potential of PEC cells by approximately 90% and approximately 36%, respectively at an optimum electron irradiation condition. The PEC responses are carefully evaluated correlating with the optical and electronic properties of electron-irradiated PCBM/TiO2 electrodes.
Nanoscale Research Letters 03/2012; 7(142). · 2.73 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: We present the synthesis and visible-light-induced catalytic activity of Ag(2)S-coupled TiO(2) nanoparticles (NPs) and TiO(2) nanowires (NWs). Through a simple wet chemical process from a mixture of peroxo titanic acid (PTA) solution, thiourea and AgAc, a composite of Ag(2)S NPs and TiO(2) NPs with sizes of less than 7 nm was formed. When the NP composite was further treated with NaOH solution followed by annealing at ambient conditions, a new nanocomposite material comprising Ag(2)S NPs on TiO(2) NWs was created. Due to the coupling with such a low bandgap material as Ag(2)S, the TiO(2) nanocomposites could have a visible-light absorption capability much higher than that of pure TiO(2). As a result, the synthesized Ag(2)S/TiO(2) nanocomposites exhibited much higher catalytic efficiency for the decomposition of methyl orange than commercial TiO(2) (Degussa P25, Germany) under visible light.
Nanotechnology 01/2010; 21(1):015703. · 3.98 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A microfocus x-ray tube that can generate x rays with the focal spot size less than 5 μm has been demonstrated using carbon nanotube (CNT) field emitters. A CNT cathode on a sharp tungsten tip, a magnetic solenoid lens, and a transmission-type x-ray target were adopted for the microfocus x-ray tube. The design characteristics and the operation performance of the microfocus x-ray tube are presented. Due to the small focal spot size, clear x-ray radiographic images of 6 μm bars and x-ray images with the magnification factor of higher than 230 were obtained.
Applied Physics Letters 04/2007; 90(18):183109-183109-3. · 3.84 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: Superhydrophobic bionic surfaces with hierarchical micro/nano structures were synthesized by decorating single-walled or multiwalled carbon nanotubes (CNTs) on monolayer polystyrene colloidal crystals using a wet chemical self-assembly technique and subsequent surface treatment with a low surface-energy material of fluoroalkylsilane. The bionic surfaces are based on the regularly ordered colloidal crystals, and thus the surfaces have a uniform superhydrophobic property on the whole surface. Moreover, the wettability of the bionic surface can be well controlled by changing the distribution density of CNTs or the size of polystyrene microspheres. The morphologies of the synthesized bionic surfaces bear much resemblance to natural lotus leaves, and the wettability exhibited remarkable superhydrophobicity with a water contact angle of about 165 degrees and a sliding angle of 5 degrees.
Langmuir 03/2007; 23(4):2169-74. · 4.19 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: A simple seed-layer assisted electrochemical deposition (ECD) route has been successfully developed for preparation of different ZnO nanostructures, and their optical and field emission properties are also studied. ZnO films, nanowires, and nanosheets could be prepared in a rational way by just controlling the ECD current density. The corresponding growth mechanisms are also discussed on the basis of the characteristics of the ZnO crystal structure and the influences of the seed-layer and ECD current density. Except for ZnO nanosheets, both the room-temperature and low-temperature photoluminescence measurements of the ZnO films and nanowire arrays show strong ultraviolet excitonic emission, which proves their good crystal quality. Detailed analysis of the field emission (FE) properties indicates that the hierarchical ZnO nanowire array shows good FE property due to their high aspect ratio, small radius curvature, and proper density.
01/2007;
-
[show abstract]
[hide abstract]
ABSTRACT: We present a novel design of an X-ray target to deliver uniform dose from an electronic brachytherapy system (EBS). This design comprises of a combination of both the reflection- and transmission-type target geometries. Monte-Carlo simulation code MCNP5 has been employed for the calculation of angular distribution of the X-ray intensity produced from various morphologies of X-ray targets. The simulation results reveal that the combinatorial target-assembly is promising and effective in achieving uniformity of X-ray emission over the entire space of solid angle of 4π in comparison to a transmission-type target that produces X-rays mainly in the forward direction and a reflection-type target that generates X-rays mostly in the backward direction. As a direct consequence of the uniformity of X-ray emission, the combinatorial target-assembly can impart a uniform dose distribution which makes it suitable as a target of an X-ray tube for EBS.Highlights► A novel X-ray target design is proposed. ► The target consists of a truncated conical reflection-type target and a transmission-type hemispherical cap. ► This combinatorial target assembly can produce X-rays with a good spatial uniformity over the entire solid angles.
Nuclear Instruments and Methods in Physics Research Section B Beam Interactions with Materials and Atoms 269(10):1053-1057. · 1.21 Impact Factor
